1. Field of the Invention
This invention relates to the art of magnetically controlled torque limiting clutches, and more particularly concerns means for automatically releasing an overload from the driving motor of a magnetic torque limiting clutch.
2. Description of the Prior Art
This invention involves improvements over the torque limiting type of magnetic clutch described in my prior U.S. Pat. No. 4,651,856 issued Mar. 24, 1987. In that patent there is described a torque limiting clutch having two or more cylindrical concentric, coaxial magnetic rings and a cylindrical permanent magnet disposed radially between the rings. Coplanar edges of the rings at one end thereof are abutted to a magnetic driven member which may be a flat plate or disk. Mechanical drive means which engage the other ends of the rings are driven rotationally by a motor. The output disk is operatively connected to a driven load via a pulley, a gear, or a driven shaft. If the clutch is overloaded, slippage occurs between the output disk and the abutted magnetic rings. This clutch is useful where the occurrence of the overload can be noticed immediately so that the motor can be stopped at once. If the motor continues to run with a blocked load or overload delivering torque up to the limit of the clutch, heat will be generated frictionally between the magnetic rings and the slipping output disk. The magnetic rings and output disk will absorb this heat quickly. With small torque limiters capable of allowing torques and speeds whose product can be one horsepower or more, the resulting heat may damage or destroy the clutch. The need therefore exists for some means to prevent the generation of this destructive heating in the event of a clutch overload.